This invention relates to a method of manufacturing a fluorescent screen, more particularly a simplified method of manufacturing a black matrix type fluorescent screen.
Generally, a black matrix type fluorescent screen of a color picture tube comprises picture elements of phosphors which luminesce in green (G), blue (B) and red (R) colors and are regularly arranged in stripe or dot triad pattern. These fluorescent picture elements are formed by photo-printing technique utilizing a photo or light-hardenable property of an ordinary photosensitive resin. More particularly, according to this method which is disclosed in U.S. Pat. No. 3,558,310 of RCA, for example, a light-hardenable type photoresist is coated on the inner wall surface of the panel of the color picture tube, and portions of the photoresist is exposed to light from a spot or linear light-source through a shadow mask such that the light will impinge upon the portions of the photoresist where the triads of phosphors are to be formed. For the purpose of approximating the locus of the electron beam to that of the exposure light, the light source is positioned at a site corresponding to the deflection center of the electron beams and a correction lens made of glass or plastics is positioned between the light source and the shadow mask. When the photoresist is developed after light exposure, the exposed portions thereof rendered hard and insoluble in a solvent due to crosslinking reaction caused by light remain to form a pattern of layers of hardened photoresist on the inner wall surface of the panel at predetermined positions. A light absorbing substance such as graphite is then coated on the surface of the photoresist layers and at voids corresponding to unexposed portions of the photoresist, dried and then treated with an oxidizing agent, hydrogen peroxide for example, to peel off the graphite films coated on the surfaces of the hardened photoresist layers together with these layers, leaving behind a pattern of black matrix. Thereafter, dots or stripes of the three color phosphors are formed on portions other than the black matrix pattern, say, corresponding to the exposed portions by conventional slurry or dusting technique.
The method of manufacturing a fluorescent screen described above is complicated and includes a number of process steps including wet coating, washing with water, development and drying, thus increasing the cost of manufacturing. Moreover, such chemicals as hydrogen peroxide are used in the etching step so that it is necessary to carefully and safely handle them.